The invention relates to plates for closing the bottom of the engine compartment of a vehicle, often referred to as xe2x80x9cunder-engine fairingsxe2x80x9d.
It is known that pedestrians constitute 3% to 10% of road accident deaths. Most of these victims are killed in built-up areas while crossing the street or while playing in it. A first regulatory test procedure was created in 1996 seeking to represent a front impact between a vehicle traveling at 40 kilometers per hour (km/h) and a pedestrian crossing the road. Three kinds of impact are defined:
impact of the head against the hood or bonnet;
thigh impact; and
leg impact.
Manufacturers will thus progressively integrate constraints concerning the development of the vehicles they make.
Leg impact relates directly to bumpers. Three criteria are measured to ensure that the tibia is not broken and that the knee is not damaged:
deceleration against the tibia must be less than 150 g, where a represents the acceleration due to gravity;
shear must be less than 6 mm; and
flexing of the knee less than 15xc2x0.
These values might be modified slightly in a forthcoming new regulation, but they will remain of the same order. When subjected to the test, a bumper is impacted in three different zones along its length. At present, no car on the market satisfies these new criteria, even though by chance some bumper zones do already give good results.
Furthermore, pedestrian impact criteria are in conflict with criteria for other standard impacts defined for bumpers:
parking impact 4 km/h; and
reparability impact (or Danner) at 15 km/h.
The second criterion in particular requires the bumper to be very stiff whereas-pedestrian impact requires a bumper that is soft.
An object of the invention is to propose a solution that is simple and of low cost to enable vehicles to satisfy criteria associated with pedestrian impact and also with other conventional impacts.
To achieve this object, the invention provides a combination of a vehicle front bumper skin and a bottom closure piece for the engine compartment and mounted behind the skin relative to the main travel direction of the vehicle, and in which the closure piece includes a front transverse section member.
Thus, the section member creates a low point of contact making it possible in the event of a pedestrian impact to initiate rotation of the leg so that the vehicle can more easily satisfy the above-mentioned criteria (deceleration, shear, flexing). Furthermore, an important advantage of this solution is that it does not load the side rails of the vehicle. If a low bearing point is established for pedestrian impact purposes by using a conventional bumper beam connected to the side rails, then, in the event of a frontal impact at 56 km/h or 64 km/h, there would be a risk of the side rail twisting before absorbing the energy of the impact, which would endanger the lives of passengers in the vehicle. The invention thus makes it possible for pedestrian impact purposes to create a low bearing point that does not load the side rails, the closure plate being conventionally fixed to the engine sub-frame.
Advantageously, the combination includes a shock absorber extending behind the skin and in front of the section member.
Advantageously, the absorber comprises a cellular material.
Advantageously, the absorber is a bottom absorber, and the combination further includes a top beam and a top shock absorber mounted behind the skin and in front of the beam, the bottom absorber being stiffer than the top absorber against a frontal impact from the front of the vehicle.
Thus, for reasons of car styling, the top absorber and its associated portion of the skin can project generally further forward from the vehicle than the bottom absorber and its associated portion of the skin. Nevertheless, in the event of a pedestrian impact, the top absorber tends to deform more than the bottom absorber, so even if first contact with the leg takes place at the top of the bumper, genuine thrust against the leg is often rapidly transferred to the bottom of the bumper. This reconciles constraints of styling with constraints of pedestrian safety.
Advantageously, the section member extends entirely in register with the skin.
This dispenses with the bottom absorber.
Advantageously, the closure piece includes two side rails extending in the travel direction of the vehicle.
This increases the stiffness of the closure piece.
Advantageously, the section member and the side rails form a U-shape when seen from above.
Advantageously, the skin is arranged in such a manner that, in profile, a portion of the skin extends in front of the section member so as to be further forward than the portion(s) of the skin which are contiguous with said portion.
The invention also provides vehicle bodywork including a combination of the invention.
The invention also provides a bottom closure piece for a vehicle engine compartment, the piece comprising a plate and presenting a general plane of symmetry, and including a section member extending transversely to the plane of symmetry.